Offshore tower



F. R. HAUBER OFFSHORE TOWER Feb. 25, 1969 Sheet of 5 Filed April 19,1967 FERDINAND R. HAUBER ATTORNEYS Feb. 25, 1969 F. R. HAUBER 3,429,133

OFFSHORE TOWER Filed April 19, 1967 INVENTOR FERDINAND R HAUBER BY 4%,f'

ATTORNEYS Feb. 25, 1969 F. R. HAUBER 3,429,133

OFFSHORE TOWER Filed April 19, 1967 Sheet ofi FIG?) INVENT ORATTORNEY-5' Feb. 25, 1969 F. R. HAUBER 3,429,133

OFFSHORE TOWER Filed April 19, 1967 Sheet INVENTOR FERDINAND R HAUBER BY5%... 11m Mu, AMA,- yum;

ATTORNEYS Feb. 25, 1969 1 F. R. HAUBER OFFSHORE TOWER Filed April 19,1967 INVENTOR FERDINAND R. HAUBER ATTORNEYS llnited States Patent TexasFiled Apr. 19, 1967, Ser. No. 631,966 US. (Tl. 6146.5 Int. Cl. 1302b17/02 8 Claims ABSTRACT OF THE DISCLOSURE A tower suitable for use inoffshore well operations and the like including a plurality of upwardlyextending, generally straight legs spaced about and disposed in aswirling pattern generally along the exterior surfaces of two mutuallyintersecting, oppositely directed, upper and lower conoidal surfaces ofrevolution developed concentrically about a single vertical axis.Connecting means rigidly support the legs in spaced relation. A hollowtoroidal base secured to the lower ends of the legs provides suflicientbuoyancy to float the tower in the water and may be selectively floodedto cause the tower to rest on the seabed.

Background of the invention This invention relates to an offshore towerof the type adapted to be positioned on the bed of a body of water withportions of the tower extending upwardly above the surface of the water,such as for example an offshore drilling platform, radar tower or thelike.

Drilling for oil in oil or gas fields situated beneath the surface of abody of water such as the sea or a lake is frequenty performed utilizinga drilling tower supported upon the seabed and extending above thesurface of the water. Some forms of drilling tower include piling drivendeep into the seabed while by contrast certain other types of drillingtower are relatively more movable, being provided with a base adapted torest on the seabed.

One example of a drilling platform of the latter type includes twoopposed parallel buoyant skids, each of which supports an upwardlyextending, converging, generally triangular side frame. The side framesare stiffened with interior cross bracing and connected together bytransverse bracing intermediate the frames. Such a platform may,however, sometimes prove unsatisfactory for a number of reasons.

For example, in violent sea conditions such structure may sometimesprove insufficiently rigid to withstand the various hydrodynamic loadsimposed upon the structure, with consequent possible hazards topersonnel and drilling apparatus on the tower.

Additionally, a skid structure of the type described, including twolinearly extending buoyant chambers, frequently has a preferreddirection of motion both when the platform is being skidded along groundsurfaces and also when the platform is being towed through the water ina floated condition. Preferred directional orientation of this type maypose serious difficulties if it is required to move the tower in adirection other than the preferred direction of motion.

A further problem may arise if, as is common, the seabed is uneven inthe location desired to be drilled. In this event, during placement ofthe tower at the desired location, portions of the skids may settle ontovertically projecting discontinuities in the seabed, thus causing thetower to come to rest at a substantial and undesirable inclination tothe vertical.

One particular situation in which conventional platforms of the typedescribed may additionally prove inadequate arises in drilling aso-called shallow field where productive oil and gas sands lie close tothe seabed. In order to provide the most effective drilling coverage forsuch a field it is usually necessary to drill a plurality of shaftsinclined to the vertical, a task which may not easily be performed withpresent conventional platforms which are usually adapted to supportdrilling apparatus for operation about a single vertical axis only.

Summary of invention It is therefore a general object of the inventionto provide an offshore tower designed to obviate problems of the typedescribed above.

It is another object of the invention to provide an offshore tower ofthe type adapted to rest on the seabed, having a particularly rigid andrugged construction to withstand excessive environmental hydrodynamicforces occasionally exerted on the water.

It is a further object of the invention to provide an offshore tower ofthe type described which may easily be settled onto the seabed in avertical orientation despite the presence of vertically extendingdiscontinuities in the seabed.

It is another object of the invention to provide an offshore tower whichmay be moved horizontally in any direction with equal facility bothduring skidding operations along the ground surfaces and during towingin a floating condition.

It is a yet another object of the invention to provide an offshore towerparticularly suitable for applications involving the drilling of anumber of adjacent bores at a substantial inclination to the verticalsuch as may be required for example in the development of shallow oilfields.

It is yet a further object of the invention to provide a particularlyconvenient method for positioning an olfshore tower at a desiredlocation.

One preferred embodiment of the invention intended to accomplish theforegoing objects comprises an offshore tower adapted to rest upon thebed of a body of water with portions of the tower extending above thesurface of the water. The tower includes a plurality of upwardlyextending, generally straight legs spaced about and disposed in aswirling pattern generally along the exterior surfaces of two mutuallyintersecting, oppositely directed upper and lower conoidal surfaces ofrevolution developed about a common vertical axis. The legs are rigidlyconnected together in spaced relation to provide a tower possessing theparticular rigidity associated inherently with conoidal structures.

The tower may be floated or settled on the seabed by respectivelyemptying or filling with water, a hollow toroidal base joining the lowerends of the legs and adapted to rest on the seabed.

The tower may be moored to the seabed by riser tubes positionedconcentrically within the legs and adapted to be driven partiallyoutwardly thereof into the underlying seabed.

In an important aspect of the invention each riser tube is adapted toguide a drilling string extending downwardly through each leg out intothe seabed at an inclination to the vertical. In this manner a number ofinclined bores may be drilled at a single site.

The drawings In accordance with these objects, an offshore tower formingone preferred embodiment of the present invention is illustrated in theaccompanying drawings in which:

FIGURE 1 is a side view of the preferred embodiment of the offshoretower shown resting on the bed of a body of water at a desired offshorelocation;

FIGURE 2 is a cross-sectional top view of a portion of the drillingplatform shown in FIGURE 1 taken along the lines 2-2 therein;

FIGURE 3 is a cross-sectional top view of a portion of the offshoretower shown in FIGURE 1, taken along the lines 33 therein, showing thebase;

FIGURE 4 is a cross-sectional side view of a portion of the offshoretower shown in FIGURE. 3, taken along the lines 44 therein, showing ariser tube projecting into the seabed;

FIGURE 5 is a cross-sectional side view of a portion of the drillingplatform shown in FIGURE 3, taken along the lines 55 therein, showing afluid-directing nozzle forming a part of the present invention;

FIGURE 6 is a cross-sectional top view of a portion of the drillingplatform shown in FIGURE 1, taken along the lines 6-6 therein, showingthe connecting frame;

FIGURE 7 is a top view on an enlarged scale of the central portion ofthe connecting frame shown in FIG- URE 6;

FIGURE 8 is a developed, partially sectional side view of a portion ofthe connecting frame shown in FIGURE 7 taken along the lines 8-8therein;

FIGURE 9 is a cross-sectional view of a portion of the drilling platformshown in FIGURE 1, taken along the lines 9-9 therein, showing the lowerframe of the jacket;

FIGURE 10 is a side view of the offshore tower forming the preferredembodiment of the invention, shown positioned on a shore prior tofloatation in an adjacent body of water;

FIGURE 11 is a side view of the offshore tower shown in FIGURE 10 duringtowing of the tower in floating condition to a desired location;

FIGURE 12 is a side view of the offshore tower shown in FIGURE 10 beingsettled onto the bed of the body of water during flushing away of anupstanding projection on the bed; and

FIGURE 13 is a side view of the drilling platform shown in FIGURE 10secured to the bed of the body of water by risers and with thesuperstructure aflixed to the drilling platform.

Detailed description Referring to FIGURE 1 of the drawings, thepreferred embodiment there shown includes a plurality of spaced straighttubular legs 4 disposed in a swirling pattern about single centralvertical axis. The pattern may best be envisaged by imagining the legsto be initially disposed in upright slightly convergent relation withthe legs equally spaced about the peripheries of two vertically spacedupper and lower, circular frames, to define a structure resembling anupended squirrel cage. If the upper frame is imagined to be subsequentlyrotated through an arc relative to the lower frame, the legs would bemoved into a swirled pattern in which the legs converge from their upperand lower ends towards a. central zone of constriction spaced a shortdistance above the midpoints of the legs. In this swirled pattern thelegs may be considered to be disposed generally about and to closelyapproach the exterior surfaces of two hypothetical, mutuallyintersecting, upper and lower cone-like surfaces of revolution(hereinafter referred to as the conoidal surfaces), developedconcentrically about the single, central vertical axis.

Referring in more detail to FIGURE 1, the lower ends of the legs 4 :arerigidly connected by a lower frame comprising a generally toroidal,compartmented, base 2 adapted to rest on the seabed. The compartmentedbase 2 possesses suflicient buoyancy to cause the tower to float but maybe selectively flooded to settle the tower onto the seabed. The legs 4,fixedly secured to and equally spaced about the compartmented base 2,extend upwardly therefrom. The lower portions of the legs 4 are disposedgenerally along and spaced equally about the exterior surface of anupwardly converging lower conoidal surface of revolution concentric withthe vertical axis in the manner previously described. Similarly theupper portions of the legs 4 are disposed generally along and spacedequally about the exterior surfaces of a downwardly converging, upperconoidal surface of revolution concentric with the vertical axis andintersecting the lower conoidal surface of revolution. The legs 4 arealso rigidly connected in spaced relation adjacent their zone of closestconvergence by a connecting frame 6 and by an upper frame 8 secured tothe upper extremities of the legs 4.

Additional bracing for the upper frame 8 is provided by a jacket,generally designated 10, which includes vertical spars 12 spacedradially from and parallel to the central axis and extending upwardlyfrom each leg to an adjacent portion of the upper frame 8. Asuperstructure 14 for supporting drilling apparatus and personnel isreleasably secured to the upper frame 8.

Referring in more detail to FIGURES l and 2, the legs 4 are spacedequally about the periphery of the toroidal base 2 and extend upwardly:and inwardly therefrom. The legs 4 mutually converge until theyintersect a horizontal plane, defined as a reference plane, designatedRP in FIG- URE 1, spaced above the lower extremities of the legs andbelow the upper extremities thereof. Above the reference plane the legs4 mutually diverge. The longitudinal axis of each leg intersects thereference plane at an intersection point radially offset from the pointof intersection of the central axis with the reference plane. Thisarrangement requires that the legs 4 be inclined inwardly of thecompartmented base 2 at their point of attachment thereto and also thatthe legs be skewed angularly to avoid intersecting the central axis.This provides a swirling pattern of the legs in which, as previouslydescribed, they may be considered to be disposed generally along theexterior surfaces of the two oppositely directed, conoidal surfaces ofrevolution.

The described swirling arrangement whereby each of the legs extendinginwardly from the base is radially offset relative to the central axisensures that the legs follow nonintersecting paths in their passagethrough the reference plane (in which the connecting frame 6 isvertically disposed) while at the same time permitting the legs toassume a generally conoidal configuration, thereby providing the towerwith the substantial added rigidity inherently associated with conicalstructures.

The previously mentioned toroidal base 2 (FIGURE 3) comprises eightsimilar tubular members 16 joined end to end to form a sealed, hollow,watertight compartmented, octagonal chamber disposed symmetrically abouta central vertical axis. It will be appreciated that the number oftubular members 16 may be varied to provide other polysidedconfigurations of the base 2. A vertically extending, central tube 18,concentric with the vertical axis of the tower, has its lower extremitypositioned centrally of the base 2 by four identical, horizontallydisposed struts 20 secured to the exterior of the shaft 18 and spaced atninety-degree intervals thereabout. The radially outward end of eachstrut 20 is secured at right angles to an adjacent portion of anadjacent one of the tubes 16.

In skidding the tower along the ground, as may be required in moving italong a shore to the waterline, the symmetrical configuration of thebase enables the tower to be moved with relatively equal facility in anydesired direction. Additionally, the symmetrical disposition of the legsof the tower about the vertical axis in conjunction with the symmetricalbase advantageously ensures that the tower, while being towed throughthe water in floating condition, has substantially no preferreddirection of motion nor any tendency to steer itself out of the line oftowing.

Each of the previously mentioned legs 4 is connected to the base 2 atthe intersection of a pair of the tubes 16. Referring to FIGURE 4, eachleg 4 is tubular and extends diametrically through the base 2, passingthrough upper and lower apertures 22 and 24 provided in the base 2 toreceive the leg 4. Each leg 4 at its lower extremity is open andterminates flush with a lower surface portion of the base 2. The base 2and each leg 4 are fixedly secured together in sealed relation about theapertures 22 and 24 to prevent the ingress of fluids into the interiorof the base 2 from the outside or from within the legs 4.

It will be appreciated that the interior portions of the tubes 16 definea peripherally extending compartmented, fluid-tight, buoyancy chamberdisposed symmetrically about the central vertical axis of the tower. Thedimensions of the tubes 16 are such that when they are filled with air,they collectively provide suflicient buoyancy to cause the tower tofloat in an upright condition in the surrounding body of water.

Conventional liquid filling and emptying means (not shown) are connectedwith each compartmented portion of the base 2 so that the base may beselectively filled with air or flooded with water to respectively floatthe tower or settle it onto the underlying seabed. The independentcomp-artmentation of the base, with each watertight compartment equippedwith its own flooding valves and air lines allows the tower to beballasted and tilted in the buoyant condition as required.

Positioned adjacent and spaced from each of the legs 4 are a pluralityof hollow, vertically extending sleeves 26 passing through an adjacentportion of each of the tubes 16 and sealed thereto top and bottom in amanner similar to that previously described for the legs 4. Each tube 26is of suflicient diameter to slidingly receive an auxiliary leg of thesame diameter as one of the legs 4 for a purpose to be describedhereinafter.

In order to enable the tower to be positively secured to the bed beneaththe body of water, each of the legs 4 receives a generally coextensive,concentric riser tube 28 of a size somewhat smaller than the interior ofthe leg 4. Each riser tube 28 may be driven downwardly and partiallyoutwardly of the leg 4 into the underlying seabed, followingconventional pile driving techniques. Grout is then pumped downwardlyintothe annulus between the riser tube 28 and the leg 4 through agrouting pipe 30, to secure them together in fixed relation. Portions ofthe grout may additionally be forced under pressure into the underlyingseabed. Details of one grouting system suitable for use in the preferredembodiment of the invention are provided in applicants copendingapplication Ser. No. 494,289, filed Aug. 27, 1965.

The operations of driving the risers outwardly from the legs andgrouting are desirably performed using conventional equipment positionedon a barge floating adjacent the tower. However, in unsettled or roughsea conditions it may be necessary to perform the riser installation andgrouting utilizing apparatus positioned on the tower itself.

In performing drilling operations, each of the riser tubes 28 is adaptedto separately receive a conventional drilling string depending fromdrilling apparatus positioned on the superstructure 14. The riser tube28 guides the drill string downwardly and outwardly of the riser tubeinto the underlying portions of the seabed to drill a bore therein at aninclination to the vertical. It will be appreciated that the leg andriser tube structure of the tower described, advantageously facilitatesdrilling of a plurality of inclined bores at a single site, as isdesirable for the most eflective development of shallow fields where theoil or gas lies relatively close to the surface.

In addition, drilling operations may also be performed utilizing thecentral tube 18 to guide the drilling string vertically downwardly intothe underlying strata.

Also disposed symmetrically about the base 2 are a plurality of radiallyoutwardly and downwardly directed nozzles 32 (FIGURES 3 and 5). Eachnozzle 32 may selectively be supplied with fluid or a mixture ofcompressed air and other suitable fluid, under high pressure from aconventional source (not shown) through a pipe 34, and is adapted todirect the fluid downwardly and radially outwardly of the base 2 in theform of a high pressure jet for purposes to be described. Although twojets mounted on each tube 16 are utilized in the preferred embodiment,it will be appreciated that any desired number or arrangement of jets 32may be provided.

Referring to FIGURES 6 and 7, the previously mentioned connecting frame6 includes a plurality of I-beams 40 fixedly secured at their radiallyinwardly extremities to the exterior of the central vertical tube 18extending radially outwardly therefrom. Each I-beam 40 (FIGURE 8)includes a vertically disposed web 42 and upper and lower horizontalflanges 44 and 46 respectively.

Each I-beam 40 at its radially outward extremity is fixedly secured tothe exterior of an adjacent one of the legs 4 with the horizontallydisposed axis of symmetry of the I-beam in longitudinal alignment with adiameter of the leg 4. The upper and lower flanges 44 and 46 of eachI-beam 40 are cut arcuately to partially embrace the curved exteriorsurface of the adjacent leg 4.

Positioned between adjacent pairs of upper flanges 44 and betweenadjacent pairs of lower flanges 46 of adjacent I-beams 40 and fixedlysecured thereto, are upper and lower, horizontally disposed, radiallyoutwardly extending, segmental decking portions 48 and 50 respectively.At their radially outer extremeties, the decking portions are configuredto embrace adjacent portions of the legs 4 and are secured thereto bywelding or the like.

Extending upwardly between the radially outer peripheries of adjacentspaced decking portions 48 and 50 thereof, and extending peripherallybetween adjacent pairs of the I-beams 40, are vertically disposed,generally flat, plate members 52. Each plate member 52 at its peripheralextremeties is configured to fit along adjacent portions of the adjacentlegs 4 and is fixedly secured thereto.

The tower also includes the previously mentioned jacket 10 to supportthe upper frame 8 on which the superstructure 14 rests. The jacket 10(FIGURES 1 and 9) includes a horizontally disposed jacket base frame 54positioned vertically intermediate the base 2 and the connecting frame6. The jacket base frame 54 includes a plurality of horizontallydisposed, tubular struts 56 fixedly secured to and extending betweenadjacent legs 4. Each of the previously mentioned vertical struts 12 is(fixedly secured to and extends vertically upwardly from one of the legs4 adjacent the intersection thereof with the struts 56.

The jacket base frame 54 also includes a plurality of horizontallydisposed, tubular, radial struts 58 fixedly secured to the exterior ofthe central vertical shaft 18 and extending radially outwardlytherefrom. Each radial strut 58 is fixedly secured at its radiallyoutward extremity to one of the legs 4 adjacent the point of connectionthereof with the struts 56.

Additional bracing for the jacket vertical struts 12 is provided by aplurality of tubular, intermediate struts 60 (FIGURES 6 and 7) disposedgenerally in the reference plane. Each of the intermediate struts 60 isfixedly secured at its radially inward end to one of the previouslymentioned vertical plates 52 of the connecting frame 6 (FIGURE 8) and isfixedly secured at its radially outward end to an adjacent one of thejacket vertical struts 12.

The previously mentioned upper frame 8 is secured to the upperextremities of the jacket vertical struts 12. Conventional decking isprovided within the interior of the frame 8 and is suitably configuredto receive the open upper ends of the legs 4 which extend through thedecking to a position generally flush with an upper surface thereof.

The previously mentioned superstructure 14 which is adapted for thesupport of personnel, drilling apparatus, and miscellaneous equipment isreleasably secured to the upper frame 8. Details of the conventionalsuperstructure 14 and of the conventional means used to secure it to theupper frame 8 do not form a part of the present invention.

Also secured to the legs 4 are a plurality of upper guide sleeves 70(FIGURES 7 and 8). Each upper guide sleeve 70 includes a-cylindricaltube 72 spaced radially outwardly of an adjacent one of the legs 4 andfixedly secured thereto by a horizontally disposed cross tube 74 havingits axis aligned with the axis of symmetry of the adjacent one of thepreviously mentioned I-beams 40. The lower sleeve 72 is of sufficientdiameter to slidably receive an auxiliary leg equal in diameter to oneof the legs 4 for a purpose to be described. Each sleeve 7 t isadditionally provided with an upwardly directed, outwardly flared, bellportion 76 to guide the auxiliary leg into the tube 72.

Each of the guide sleeves 70 is axially aligned with one of thepreviously mentioned sleeves 26 extending through the base member 2. Theaxes of each guide sleeve 70 and of its respectively aligned sleeve 26are parallel to that of the adjacent leg 4.

In drilling particularly prolific oil or gas fields it is oftenadvantageous to increase the number of bores drilled at one particularsite. For this purpose, the guide sleeves 72 and the lower sleeves 26are provided as they permit an auxiliary set of legs 4 to be installedabout the tower, by sliding each of the auxiliary legs 4 through one ofthe various aligned pairs of guide sleeves 72 and lower sleeves 26, andsubsequently fixedly securing the auxiliary legs thereto. A second setof bores may be then drilled through the auxiliary legs in a mannersimilar to that previously described. In this manner, drilling coverageprovided at one location of the tower may be easily doubled.

In installing the tower, various prefabricated elements of the tower areassembled on a shore adjacent the body of water. After the tower hasbeen assembled, it is skidded toward the water. The generally toroidalconfiguration of the base 2 permits the device to be skidded withrelatively equal facility in any desired direction. Once the tower hasbeen positioned adjacent the edge of the water (FIGURE 10) with the basein an air-filled condition, the tower is floated into the water usingknown techniques. The tower is then towed (FIGURE 11) to the desiredlocation. The base may then be partially flooded to cause the tower tosettle towards the sea. If, as shown in FIGURE 12, one portion of thebase encounters a portion of the seabed projecting above the generalhorizontal level of the remainder of the bed, the tower will settle inan inclined position. At this time, with the tower still in asemibuoyant condition, pressure fluid is selectively directed throughthe jets 32 disposed adjacent the underlying projecting portions of theseabed to flush them away. As the tower attains a level position,pressure fluid to the selected jets is cut off and the base 2 fullyflooded to settle the tower on the seabed with the upper portions of thetower projecting above the water level. In a final operation (FIGURE 13)the riser tubes 28 are driven into the seabed as previously described,to secure the tower firmly to the seabed.

It will be seen that in constructing an oifshore tower according to thepresent invention, a tower uniquely suitable for use in offshoredrilling and other like operations is provided.

In particular, the disposition of the legs about the surfaces of twooppositely directed intersecting conoidal surfaces provides the towerwith the considerable added rigidity known to be characteristic ofconical structures.

In addition, the symmetrical configuration of the base and thesymmetrical disposition of the legs about the vertical axis ensures thatthe tower has no preferred direction of motion either during skiddingalong the ground or during towing through the water, with the desirableresult that the tower may be moved with substantially equal facility inany desired direction.

Another important advantage is afforded by the jets disposed about thebase, which enable projecting portions of the seabed to be flushed awayby the application thereto of high pressure fluid so that the tower maybe enabled to settle on the seabed in a desired, vertically uprightposition.

A further advantage arises from the provision of a plurality of adjacentlegs each of which may be used to guide drilling apparatus at aninclined angle, thus permitting a number of inclined bores to be drilledon one site, as is particularly desirable in drilling shallow fieldswhere the oil or gas lies relatively close to the surface.

Although the invention is described with reference to one preferredembodiment, it will be apparent to those skilled in the art thatadditions, deletions and modifications, substitutions and other changesnot specifically described and illustrated in this embodiment, may bemade which will fall within the purview of the appended claims.

I claim:

1. An offshore tower adapted to rest upon the bed of a body of waterwith portions of the tower extending above the surface of the water,said tower comprising:

a plurality of upwardly extending, generally straight tubular legsspaced about a central vertical axis, said legs intermeditae the endsthereof intersecting a defined generally horizontal reference plane,said legs mutually diverging in directions upwardly and downwardly fromsaid reference plane;

means rigidly connecting said legs for supporting said legs in fixedspaced relation to each other;

a base rigidly connecting the lower extremity of said legs, said baseadapted to rest upon the bed of the body of water;

a plurality of hollow riser tubes positioned concentrically within saidlegs, each said riser tube adapted to be driven partially outwardly ofthe associated one of said legs into the bed of the body of water tomoor thereto said base, each said riser tube adapted to receive a drillstring to direct the associated drill string from one side of the towerthrough a path generally centrally of the tower to the other sidethereof, said riser tube guiding the drill string outwardly of said baseand downwardly into the bed at an inclination to the vertical; and

means for fixedly connecting each said riser tube with the associatedone of said legs subsequent to mooring of said base to the bed.

2. An offshore tower adapted to rest upon the bed of a body of waterwith portions of the tower extending above the surface of the water,said tower comprising:

a plurality of upwardly extending, generally straight legs spaced aboutand disposed in a swirling pattern generally along the exterior surfacesof two mutually intersecting, oppositely directed upper and lowerconoidal surfaces of revolution developed concentrically about a commonvertical axis, the lower extremities of said legs being disposed in agenerally horizontal base plane;

means rigidly connecting said legs for supporting said legs in fixedspaced relation to each other;

a base secured to and rigidly connecting the lower ex tremities of saidlegs, said base adapted to rest on the bed of the body of water, saidbase having a generally toroidal periphery disposed symmetrically aboutsaid vertical axis;

a plurality of nozzles secured to and disposed about the periphery ofsaid base directed downwardly and outwardly therefrom; and

means for selectively directing fluid under pressure outwardly throughselected ones of said nozzles to flush away underlying raised portionsof the bed of the body of water to enable said base to rest horizontallyupon the bed.

3. An oifshore tower adapted to rest upon the bed of a body of waterwith portions of the tower extending above the surface of the water,said tower comprising:

a plurality of upwardly extending, generally straight legs spaced aboutand disposed in a swirling pattern generally along the exterior surfacesof two mutually intersecting, oppositely directed upper and lowerconoidal surfaces of revolution developed concentrically about a commonvertical axis, the lower extremities of said legs being disposed in agenerally horizontal base plane;

means rigidly connecting said legs for supporting said legs in fixedspaced relation to each other;

a base secured to and rigidly connecting the lower extremities of saidlegs, said base adapted to rest on the bed of the body of water, saidbase having a generally toroidal periphery disposed symmetrically aboutsaid vertical axis;

a plurality of guide tubes, each of said guide tubes being secured toand spaced radially outwardly from each of said legs;

said base including a plurality of apertures extending through said basemember adjacent each of said legs;

each of said guide tubes having a central passageway axially alignedwith one of said apertures, said passageway and said aperture havingtheir axes aligned generally parallel to the axis of the adjacent saidsaid guide tubes and said passageways adapted to receive auxiliary legmembers in spaced relation parallel to adjacent each of said legs.

4. An offshore tower adapted to rest upon the bed of a body of waterwith portions of the tower extending above the surface of the water,said tower comprising:

a plurality of upwardly extending, generally straight legs spaced aboutand disposed in a swirling pattern generally along the exterior surfacesof two mutually intersecting, oppositely directed upper and lowerconoidal surfaces of revolution developed concentrically about a commonvertical axis, the lower extremities of said legs being disposed in agenerally horizontal base plane;

means rigidly connecting said legs for supporting said legs in fixedspaced relation to each other;

a base secured to and rigidly connecting the lower extremities of saidlegs, said base adapted to rest on the bed of the body of water, saidbase having a generally toroidal periphery disposed symmetrically aboutsaid vertical axis;

said base further including,

a hollow, peripherally extending chamber disposed symmetrically aboutthe axis; and

means connected with said chamber for selectively filling and emptyingsaid chamber with water, said chamber in an emptied condition providingsufficient buoyancy to cause said tower to float in the water.

5. An ofishore tower defined in claim 4 wherein:

each of said legs is tubular having a hollow interior and open upper andlower extremities, said base further including sealing means forpreventing fiuid communication between the interior of each said leg andsaid hollow chamber in said base.

6. An offshore tower adapted to rest upon the bed of a body of waterwith portions of the tower extending above the surface of the water,said tower comprising:

a plurality of upwardly extending, generally straight legs spaced aboutand disposed in a swirling pattern generally along the exterior surfacesof two mutually intersecting, oppositely directed upper and lowerconoidal surfaces of revolution developed concentrically about a commonvertical axis, the lower extremities of said legs being disposed in agenerally horizontal base plane;

means rigidly connecting said legs for supporting said legs in fixedspaced relation to each other;

a base secured to and rigidly connecting the lower extremities of saidlegs, said base adapted to rest on the bed of the body of water, saidbase having a generally toroidal periphery disposed symmetrically aboutsaid vertical axis; and

tubular riser means within at least one of said legs selectively movablepartially outwardly and downwardly of said leg and adapted to penetratean underlying portion of the bed to secure said base to the bed.

7. An offshore tower as defined in claim 1 wherein each said riser meansincludes an axially extending interior passageway adapted to guide adrilling string positioned interiorly of said riser means outwardlythereof into the underlying bed.

8. An oflshore tower as defined in claim 4 wherein said chamber in saidbase is compartmented.

References Cited UNITED STATES PATENTS 2,496,532 2/1950 Gross 61-4652,940,266 6/1960 Smith 6146.5 3,014,347 12/1961 Knapp 61-465 3,093,1676/1963 McCammon 61-465 X 3,138,932 6/1964 Kofahl et al. 61-46.53,209,544 10/1965 Borrmann 61-465 3,315,473 4/1967 Hauber et a1 61-465FOREIGN PATENTS 697,767 6/ 1930 France. Ad. 63,338 3/1955 France.

JACOB SHAPIRO, Primary Examiner.

U.S. Cl. X.R.

